Current therapy of the Ichthyoses is purely symptomatic, and often irrational; e.g., when removal of excess scale interferes with homeostatic responses that allow patients to survive in a harsh, terrestrial environment. At the other extreme, corrective gene therapy, though seductive in concept, remains a distant dream, with many potential pitfalls. Our approach will be first, to identify pathogenic mechanisms in patients, and then to assess whether this new information can be translated into readily-deployable, topical therapy in disease-appropriate animal models. Initially, we will study Ichthyosis pathogenesis (in patients and relevant animal models) with inherited, syndromic disorders of distal cholesterol metabolism (Group I disorders) where the cutaneous phenotype can range from severe (as in CHILD syndrome, lathosterolosis, and SC4MOL deficiency), to moderately-severe (as in CHH), or mild-to-inapparent (as in SLOS and desmosterolosis). Then, we will translate mechanistic insights into potentially-effective therapies in relevant animal models. This pathogenesis-based approach then will be extended to patients (and animal models) of other syndromic disorders of lipid metabolism (Group II). Following identification and optimization of effective therapy in the animal models, we will launch clinical studies for these patients, as part of a parallel grant proposal. If successful, this approach should initiate a paradigm shift in how many of the Ichthyoses will be treated in the future. Finally, since the cutaneous phenotype reflects pathogenic mechanisms that also are on-going in extracutaneous tissues, successful pathogenesis-based therapy for the Ichthyoses could point to comparable approaches to treat/prevent the extracutaneous manifestations of these disorders.